Designation A745/A745M − 15 Standard Practice for Ultrasonic Examination of Austenitic Steel Forgings1 This standard is issued under the fixed designation A745/A745M; the number immediately following[.]
Designation: A745/A745M − 15 Standard Practice for Ultrasonic Examination of Austenitic Steel Forgings1 This standard is issued under the fixed designation A745/A745M; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A superscript epsilon (´) indicates an editorial change since the last revision or reapproval A531/A531M Practice for Ultrasonic Examination of Turbine-Generator Steel Retaining Rings A788/A788M Specification for Steel Forgings, General Requirements A965/A965M Specification for Steel Forgings, Austenitic, for Pressure and High Temperature Parts A1049/A1049M Specification for Stainless Steel Forgings, Ferritic/Austenitic (Duplex), for Pressure Vessels and Related Components E317 Practice for Evaluating Performance Characteristics of Ultrasonic Pulse-Echo Testing Instruments and Systems without the Use of Electronic Measurement Instruments E428 Practice for Fabrication and Control of Metal, Other than Aluminum, Reference Blocks Used in Ultrasonic Testing 2.2 American Society for Nondestructive Testing Document:4 SNT-TC-1A Recommended Practice for Nondestructive Personnel Qualification and Certification Scope* 1.1 This practice covers straight and angle beam contact, pulse-echo ultrasonic examination of austenitic steel forgings produced in accordance with Practice A388/A388M and Specifications A965/A965M and A1049/A1049M 1.2 Ultrasonic examination of nonmagnetic retaining ring forgings should be made to Practice A531/A531M rather than this practice 1.3 Supplementary requirements of an optional nature are provided for use at the option of the purchaser The supplementary requirements shall apply only when specified individually by the purchaser in the purchase order or contract 1.4 This practice is expressed in inch-pound and SI units; however, unless the purchase order or contract specifies the applicable “M” specification designation (SI units), the inchpound units shall apply The values stated in either inch-pound units or SI units are to be regarded separately as standard Within the practice, the SI units are shown in brackets The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other Combining values from the two systems may result in nonconformance with the standard 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use Ordering Information 3.1 When this practice is to be applied to an inquiry or purchase order, the purchaser shall furnish the following information: 3.1.1 Quality level of examination (see Section 12) 3.1.2 Additional requirements to this practice 3.1.3 Applicability of supplementary requirements (see Supplementary Requirements section) 3.1.4 Supplementary requirements, if any Referenced Documents 3.2 When specified, the manufacturer shall submit an examination procedure for purchaser approval that shall include, but not be limited to, a sketch of the configuration as presented for ultrasonic examination showing the surfaces to be scanned, scanning directions, notch locations and sizes (if applicable), extent of coverage (if applicable), and an instruction listing calibration and inspection details and stage of manufacture 2.1 ASTM Standards:3 A388/A388M Practice for Ultrasonic Examination of Steel Forgings This practice is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloysand is the direct responsibility of Subcommittee A01.06 on Steel Forgings and Billets Current edition approved May 1, 2015 Published May 2015 Originally approved in 1977 Last previous edition approved in 2012 as A745/A745M – 12 DOI: 10.1520/A0745_A0745M-15 For ASME Boiler and Pressure Vessel Code applications see related Specification SA-745/SA-745M in Section II of that Code For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website Apparatus 4.1 Electronic Apparatus—A pulse-echo instrument permitting inspection frequencies of 1, 2.25, and MHz is required Available from American Society for Nondestructive Testing (ASNT), P.O Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org *A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States A745/A745M − 15 4.4.3 Other search units, including frequencies other than those listed in Section 8, may be used for evaluating and pinpointing indications of discontinuities The accuracy of discontinuity amplitude analysis using this practice involves a knowledge of the true operating frequency of the complete inspection system One of the best ways to obtain the desired accuracy is by use of a tuned pulser and narrow band amplifier of known frequency response, with either a broadband transducer, or a narrow-band tuned transducer of known and matching frequency 4.1.1 Apparatus Qualification and Calibration—Basic qualification of the ultrasonic test instrument shall be performed at intervals not to exceed 12 months or whenever maintenance is performed that affects the equipment function The date of the last calibration and the date of the next required calibration shall be displayed on the test equipment 4.1.2 The horizontal linearity shall be checked on a distance calibration bar using the multiple order technique (see Practice E317) The horizontal linearity shall be 62 % of the metal path 4.1.3 The accuracy of the linearity shall be checked by ultrasonically verifying the thickness of the component in at least one location beyond the near field of the transducer If necessary, minor adjustments for differences in the ultrasonic velocities between the calibration bar and the forging shall then be made 4.5 Couplant—A suitable couplant having good wetting characteristics shall be used between the transducer and the examination surface The same couplant shall be used for calibration and examination 4.6 Reference Blocks: 4.6.1 All ultrasonic standard reference blocks shall be in accordance with the general guidelines of Practice E428 However, absolute conformance to Practice E428 is not mandatory due to the nature of the material covered by this practice 4.6.2 The reference block grain size, as measured by the relative acoustic penetrability of the reference blocks, should be reasonably similar to the forging under examination However, it must be recognized that large austenitic forgings vary considerably in acoustic penetrability throughout their volume due to variations in grain size and structure Reference blocks should be chosen that reasonably approximate the average penetrability of the forging under examination Supplementary blocks of coarser or finer grain may be used for evaluation of indications as covered in Section 11 4.6.3 As an alternative method, where practicable, the appropriate size of reference hole (or holes) or notches may be placed in representative areas of the forging for calibration and examination purposes when removed by subsequent machining When holes or notches are not removed by subsequent machining, the purchaser must approve the location of holes or notches 4.2 Amplifier—The amplifier and display shall provide linear response within 62 %, up to 100 % of full screen height 4.2.1 Amplifier Calibration—An amplifier vertical linearity check shall be made prior to performing the test by observing a multiple order pattern from a calibration block using a 2.25 MHz transducer (see Practice E317) The first back reflection shall be set at 100 % of full screen height The higher order back reflections, 10 % and higher in amplitude, shall also be positioned on the screen and their amplitudes noted The first back reflection shall be reduced to 50 % and then 25 % of full screen height The amplitudes of the higher order back reflections shall be noted at each step The vertical linearity will be considered acceptable if the signal heights of the higher order reflections decrease in proportion to the decrease set for the first back reflection The maximum acceptable error for the decrease of the higher order reflections is the greater of 65 % of the expected back reflection height or 62 % of full screen height Personnel Requirements 5.1 Personnel performing the ultrasonic examinations to this practice shall be qualified and certified in accordance with a written procedure conforming to Recommended Practice No SNT-TC-1A or another national standard that is acceptable to both the purchaser and the supplier Forging Conditions 6.1 Forgings shall be ultrasonically examined after heat treating 4.3 Signal Attenuator—The instrument shall contain a calibrated gain control or signal attenuator that meets the requirements of Practice E317 (in each case, accurate within 65 %) that will allow indications beyond the linear range of the instrument to be measured It is recommended that these controls permit signal adjustments up to 25 to (28 dB) 6.2 The surfaces of the forging to be examined shall be free of extraneous material such as loose scale, paint, dirt, etc 6.3 The surface roughness of scanning surfaces shall not exceed 250 µin [6 µm] unless otherwise stated in the order or contract where the definition for surface finish is as per Specification A788/A788M 4.4 Search Units: 4.4.1 The maximum nominal active area of 11⁄2 in.2 [970 mm2] with 1⁄2-in [13 mm] minimum to 11⁄8-in [30 mm] maximum dimensions or 3⁄4-in [20 mm] diameter minimum dimension shall be used for straight-beam scanning 4.4.2 Angle-beam scanning transducers shall have a nominal active area of 1⁄2 to in.2 [325 to 650 mm2] The search unit used for angle-beam examination shall produce a beam angle of 30 to 70° in the material 6.4 The forgings shall be machined to a simple configuration, that is, rectangular or parallel or concentric surfaces where complete volumetric coverage can be obtained 6.5 In certain cases, such as with contour forged parts, it may be impractical to assure 100 % volumetric coverage Such forgings shall be examined to the maximum extent possible A procedure indicating the extent of examination coverage shall be submitted for the purchaser’s approval (see 3.2) A745/A745M − 15 Procedure Straight-Beam Examination 7.1 Perform the ultrasonic examination after heat treatment when the forging is machined to the ultrasonic configuration but prior to drilling holes, cutting keyways, tapers, grooves, or machining sections to final contour 9.1 Method of Calibration: 9.1.1 Perform calibration for straight-beam examination on the flat-bottom hole size determined by the applicable quality level (see Section 12) 9.1.2 Determine the calibration method by the test metal distance involved 9.1.2.1 Thicknesses up to in [150 mm] may be examined using either the single-block or the distance-amplitude curve calibration method (a) Single-Block Method—Establish the test sensitivity on the reference standard representing the forging thickness Drill flat-bottom holes normal to the examining surface, to midsection in material up to 1.5 in [40 mm] in thickness and at least 0.75 in [20 mm] in depth but no deeper than midsection in thicknesses from 1.5 to in [40 to 150 mm] Make evaluations of indications at the estimated discontinuity depth at which they are observed using supplementary reference standards, if necessary (b) Distance-Amplitude-Curve Correction Method— Establish the test sensitivity on the reference standard whose metal travel distance represents the greater metal travel distance of the part under examination, within 61 in [25 mm] 9.1.2.2 Examine thicknesses from to 24 in [150 to 600 mm] using the distance-amplitude calibration method Calibration to 1⁄2 thickness test metal distance may be used provided examinations from two opposing surfaces are made 9.1.2.3 For metal travel distances over 24 in [600 mm], perform one of the following examinations: (a) Perform a back-reflection examination from at least one surface to QL-5 (see 12.1.1) or to a purchaser-approved procedure (see 3.2) (b) On hollow-round forgings with wall thicknesses less than in [200 mm], perform an axial angle-beam scan in place of the straight-beam scan from the end surfaces Calibration for this scan may be established on the existing axial notches required for the circumferential scan or on transverse oriented notches installed specifically for axial angle beam 7.2 To ensure complete coverage of the forging volume when scanning, index the search unit with at least 15 % overlap with each pass 7.3 The scanning rate shall not exceed in [150 mm]/s 7.4 Scan all regions of the forging in at least two perpendicular directions to the maximum extent possible 7.5 Scan disk and disk-type forgings using a straight beam from at least one flat face and radially from the circumference when practicable For the purposes of this practice, a disk is a cylindrical shape where the diameter dimension exceeds the height dimension Disk-type forgings made as upset-forged “pancakes” shall be classified as disks for inspection purposes although at the time of inspection, the part may have a center hole, counterturned steps, or other detail configuration 7.6 Scan cylindrical sections, ring and hollow forgings from the entire external surface (sides or circumference), using the straight-beam technique, and scan the forging in the axial direction to the extent possible When the length divided by the diameter ratio (slenderness ratio) exceeds to (or axial length exceeds 24 in [600 mm]), scan axially from both end surfaces to the extent possible If axial penetration is not possible due to attenuation, angle-beam examination directed axially may be substituted in place of axial straight beam Examine ring and hollow forgings having an outside-diameter to inside-diameter ratio of less than to and a wall thickness less than in [200 mm] by angle-beam techniques from the outside diameter or inside diameter, or both, using full node or half-node technique (see 10.1.2 and 10.1.3) as necessary to achieve either 100 % volumetric coverage or the extent of coverage defined by an approved procedure (see 3.2) Examination Frequency 9.2 Calibration Procedure—Over an indication-free area of the forging and with the proper test frequency, adjust the amplitude of the back reflection to the maximum limit of vertical linearity of the instrument The adjusted instrument sensitivity display shall be the primary calibration reference for both the single-block and multiple-block calibration methods If, at this gain setting, the amplitude response from the flat-bottom hole in the longest calibration block is not equal to or greater than 0.5 in [13 mm] sweep-to-peak, adjust the instrument gain further to obtain a 0.5-in [13 mm] sweep-topeak minimum response To complete the distance-amplitude correction curve, determine the remaining points defining the shape of the curve at this adjusted gain setting and mark the curve on the shield of the cathode ray tube or plot on a graph At least three blocks shall be used with test metal distances of in [75 mm] 1⁄2 T, and T However, the distance between any of the test blocks shall be 11⁄2 in [40 mm] minimum If indications closer than in [75 mm] from the initial pulse must be evaluated, an additional block with 11⁄2 in [40 mm] test metal distance shall be used This is the fixed reference 8.1 Perform all ultrasonic examination at the highest frequency practicable (as specified in 8.1.1, 8.1.2, or 8.1.3) that will adequately penetrate the forging thickness and resolve the applicable reference standard Include in the ultrasonic examination report the examination frequency used Determine the test frequency at the time of actual examination by the following guidelines: 8.1.1 The nominal test frequency shall be 2.25 MHz Use of this frequency will generally be restricted due to attenuation 8.1.2 One megahertz is acceptable and will be the frequency generally applicable 8.1.3 When necessary, due to attenuation, 0.5-MHz examination frequency may be used The purchaser may request notification before this lower frequency is employed 8.1.4 In the event that adequate penetration of certain regions is not possible even at 0.5 MHz, alternative nondestructive examination methods (such as radiography) may be employed to ensure the soundness of the forging by agreement between the purchaser and the manufacturer A745/A745M − 15 whether they result from defects or grain structure It is desirable to have several sets of calibration blocks with varying degrees of grain coarseness so that the attenuation of the defective area can be reasonably matched with a test block for a more accurate minimum defect size estimation Due to the normal wide variation in attenuation throughout a given large austenitic forging, it is permissible to evaluate rejectable indications on the basis of alternative calibration blocks that compare more reasonably in attenuation to the defect area It is also permissible to insert reference holes into representative areas of the forging itself, with the approval of the purchaser, to be used for calibration and evaluation of indications Loss of back reflection results not only from internal discontinuities but also from coarse or nonuniform grain structures, variations in coupling, nonparallel reflecting surfaces, and other factors that must be considered before concluding that loss of back reflection resulted from discontinuities against which all indications shall be evaluated at the maximum obtainable response at whatever depth the indications are observed This will constitute an acceptable examination if there are no indications exceeding the acceptance limits In large forgings, it is expected that a portion of the distanceamplitude curve will be above the vertical linearity limits of the instrument If an indication appears in this area, readjust the instrument through the use of a calibrated gain control or through recalibration to the initial calibration level to bring the appropriate portion of the presentation on screen for evaluation of that specific area NOTE 1—When flat surfaced reference block calibration is used for examination of forgings with surface curvature, compensation for curvature shall be made and the method for curvature correction shall be a matter of agreement between the producer and the purchaser For diameters 80 in [2000 mm] and over, no correction factor is required 10 Angle-Beam Examination 10.1 Ring and hollow round forgings, as defined in 7.6, shall be angle-beam examined from their outer periphery in both circumferential directions employing the following method of calibration: 10.1.1 Notches of 1.25 in [30 mm] maximum surface length, with the length perpendicular to sound propagation; depth based on quality level (Section12), either rectangular with a width not greater than twice its depth or 60° minimum to 75° maximum included angle, located in the forging so as to produce no interference with each other, shall be used as calibration standards 10.1.2 Determine the response from the inside and outside diameter calibration notches with the search unit positioned to produce the maximum response from each notch Adjust the sensitivity of the ultrasonic equipment so that the indication from the notch at the greatest test metal distance is at least 0.5 in [13 mm] sweep-to-peak Draw a straight line connecting the peaks of the responses obtained from the inside and outside diameter notches This shall be the primary reference line This procedure is considered full node calibration 10.1.3 In the event that a response of at least 0.5 in [13 mm] sweep-to-peak cannot be obtained from both the inside and outside diameter notches, calibrate from both the outer periphery (the outside diameter surface) and the inside diameter surface Adjust the sensitivity of the ultrasonic equipment so that the indication from the notch in the opposite surface is at least 0.5 in [13 mm] sweep-to-peak in magnitude This procedure is considered half-node calibration Axial angle beam may be substituted for straight beam from the end surfaces, when specified 12 Quality Levels for Acceptance 12.1 One of the following quality levels may be specified by the purchaser: 12.1.1 Straight Beam: 12.1.1.1 Material producing an indication response whose maximized amplitude equals or exceeds 100 % of the primary reference or distance-amplitude correction curve at the estimated discontinuity depth shall be considered unacceptable (a) QL-1—A distance-amplitude curve shall be based upon the amplitude response from No flat-bottom hole (8⁄64 in [3 mm]) (b) QL-2—A distance-amplitude curve shall be based upon the amplitude response from No 16 flat-bottom hole 16⁄64 in [6 mm]) (c) QL-3—A distance-amplitude curve shall be based upon the amplitude response from No 24 flat-bottom hole 24⁄64 in [10 mm]) (d) QL-4—A distance-amplitude curve shall be based upon the amplitude response from No 32 flat-bottom hole 32⁄64 in [13 mm]) (e) QL-5—A back reflection examination shall be performed guaranteeing freedom from complete loss of back reflection accompanied by an indication of a discontinuity For this purpose, a back reflection of less than % of full screen height shall be considered complete loss of back reflection 12.1.1.2 The applicable quality level will necessarily vary with test metal distance, purchasers’ requirements, and the type and size of forging involved Large disks, rings, or solid forgings and complex forgings present extraordinary problems and quality level application shall be a matter of agreement between the manufacturer and the purchaser For general guidance purposes, the following list of test metal distances versus quality level attainable is provided for general information (a) QL-1—Generally practical for thicknesses up to in [75 mm] (b) QL-2—Generally practical for thicknesses up to in [200 mm] (c) QL-3—Generally practical for thicknesses up to 12 in [300 mm] NOTE 2—Long cylinders or cylinders with small inside diameters are difficult to examine from the inside diameter surface Normally, neither inside diameters smaller than 18 in [450 mm] nor long cylinders exceeding 36 in [900 mm] in length are scanned from the inside diameter surface 11 Evaluation of Material 11.1 Coarse-grained austenitic materials frequently display sweep noise, particularly when an examination is performed at high sensitivities For this reason, it is important to critically scrutinize reportable and rejectable indications to determine A745/A745M − 15 13 Reportable Indications (d) QL-4—Generally practical for thicknesses up to 24 in [600 mm] (e) QL-5—Frequently practical for thicknesses over 24 in [600 mm] 12.1.2 Angle Beam—Material producing indications with amplitudes equal to or exceeding the primary referenceacceptance line (full node calibration; see 10.1.2) at the estimated discontinuity depth observed shall be considered unacceptable When examining with only one calibration notch (half node calibration; see 10.1.3), material containing indications of discontinuities equal to or exceeding the notch indication amplitude shall be considered unacceptable 12.1.2.1 QA-1 Angle beam reference acceptance shall be based on a notch depth of % of the thickness of the forging at the time of examination 12.1.2.2 QA-2 Angle beam reference acceptance line shall be based on a notch depth of the lesser of % of the thickness of the forging at the time of inspection, or 3⁄4 in [19.05 mm] 13.1 A record that shows the location and orientation of all indications or groups of indications with amplitudes as defined below shall be submitted to the purchaser for information 13.1.1 Indications accompanied by a loss of back reflection of 75 % of screen height Similar loss in back reflection without indications shall be scanned at lower frequencies; if unsuccessful, the area shall be reported as “not inspected.” 13.1.2 Indications distinct from the normal noise level and traveling to the left or right on the cathode ray tube with movement of the transducer 1.0 in [25 mm] or more over the surface of the forging 13.1.3 Indications equal to or exceeding 50 % of the applicable reference acceptance curve (both straight and angle beam) 14 Keywords 14.1 acceptance criteria; austenitic forgings; contact method; ultrasonic examination SUPPLEMENTARY REQUIREMENTS Supplementary requirements shall apply only when specified by the purchaser in the inquiry or order Details of these supplementary requirements shall be agreed upon between the manufacturer and the purchaser S1 Angle Beam Calibration Based on Final Thickness S2 Surface Finish S1.1 The depth of the calibration notch (see 12.1.2) shall be based upon the final ordered thickness of the forging rather than the thickness at the time of inspection S2.1 The surface finish shall not exceed 125 µin (3.17 µm) where the definition for surface finish is as per Specification A788/A788M SUMMARY OF CHANGES Committee A01 has identified the location of selected changes to this standard since the last issue (A745/A745M – 12) that may impact the use of this standard (Approved May 1, 2015.) (1) Added definition of surface finish by reference to Specification A788/A788M in 6.3 and S2 ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website (www.astm.org) Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/